Recent developments in data storage, most particularly development of optical disks, have led to new problems with respect to marketing methods for data bases stored thereon. It is now feasible to encode enormous amounts of data onto a single optical disk and provide a reasonably economical laser disk reader for accessing the data. For example, it is now possible to reproduce all of the information concerning all of the airports of the world into a single disk. This information includes essentially all physical data required for navigation of airplanes including such things as the locations and frequencies of radio beacons, their bearings from other beacons, physical descriptions of airports, including sufficient information to enable a video picture of the approach to the airport to be displayed to a pilot, together with depiction of landmarks, mountains, rivers, towers, buildings, roads, railway lines, and all other relevant information. As mentioned, all this information can now be stored on a single optical disk, and it is or will shortly be within the skill of the art to provide a disk reader with display sufficiently compact to fit into the cockpit of an airplane. In this way, the pilot may be provided with all the information requied for navigation, including a video "picture" of the air port at which he is to land, right in the cockpit of his airplane. However, preparation of this massive data base for storage on an optical disk is a major task. Similarly, creation of the disk itself is quite complicated, involving as it does the creation of "masters", intermediate stages in the finishing of the disks, as well as their production, storage, and distribution. For this reason, manufacturers would prefer that as few different disks as possible be manufactured, so that the costs of production of the disks could be amortized over as large a customer base as possible.
It will be appreciated, however, that some pilots only fly in certain areas, for example, New England, while other fly nationwide, and still other worldwide. Provision of a single version of a disk with all the data on it would necessitate that New England pilots would have to purchase a data base containing data on foreign countries, as well as on the remainder of the United States. Ordinarily this would mean that all pilots would pay the same price for the data base. However, it would seem inequitable to require pilots requiring access to only a small portion of the data base to pay the same as pilots desiring access to larger portions or all of the data base; and of course the pilots would prefer to only purchase that portion of the data base which they might use.
In order that a single version of the disk can be manufactured, containing the complete data base, but wherein the price paid for the disk can be determined in accordance with the portion of the data actually needed by the user, some means for prevention of access of the user to other portions of the data base should be provided, and this is an object of this invention.
It is a further object of the invention to provide an optical disk reader for reading data from an optical disk, comprising means for control of the access of the user to predetermined portions of the data base, such that the manufacturer of the disk has control over the access of users to specific areas of the disk, and in which neither the disk reader apparatus, the disk itself, nor their manufacture is unduly complicated by the provision of the limited access feature.